Method and apparatus for combining space-frequency block coding, spatial multiplexing and beamforming in a mimo-ofdm system

ABSTRACT

A method and apparatus for combining space-frequency block coding (SFBC) in a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system is described herein. A transmitter, according to one embodiment, may include four antennas and circuitry configured to transmit in an OFDM symbol time period using both frequency diversity and SFBC. For frequency diversity at least one first data element may be repeated producing at least two second data elements and the two second data elements are transmitted using different subcarriers. For space frequency block coding, a pair of third data elements may be space frequency block coded producing four fourth data elements. The four fourth data elements may be transmitted using two subcarriers and only two of the four antennas.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/369,768, filed on Feb. 9, 2012, which is a continuation of U.S.patent application Ser. No. 11/254,358, filed on Oct. 20, 2005 whichissued as U.S. Pat. No. 8,130,855 on Mar. 6, 2012, which claims thebenefit of U.S. Provisional Patent Application No. 60/627,210 filed Nov.12, 2004, the contents of which are hereby incorporated by reference asif fully set forth.

FIELD OF INVENTION

The present invention is related to wireless communication systems. Moreparticularly, the present invention is related to a method and apparatusfor transmission diversity in such systems.

BACKGROUND

OFDM is a data transmission scheme where data is split into a pluralityof smaller streams and each stream is transmitted using a sub-carrierwith a smaller bandwidth than the total available transmissionbandwidth. The efficiency of OFDM depends on choosing these sub-carriersorthogonal to each other. The sub-carriers do not interfere with eachother while each carrying a portion of the total user data.

An OFDM system has advantages over other wireless communication systems.When the user data is split into streams carried by differentsub-carriers, the effective data rate on each sub-carrier is muchsmaller. Therefore, the symbol duration is much larger. A large symbolduration can tolerate larger delay spreads. Thus, it is not affected bymultipath as severely. Therefore, OFDM symbols can tolerate delayspreads without complicated receiver designs. However, typical wirelesssystems need complex channel equalization schemes to combat multipathfading.

Another advantage of OFDM is that the generation of orthogonalsub-carriers at the transmitter and receiver can be done by usinginverse fast Fourier transform (IFFT) and fast Fourier transform (FFT)engines. Since the IFFT and FFT implementations are well known, OFDM canbe implemented easily and does not require complicated receivers.

MIMO refers to the type of wireless transmission and reception schemewhere both a transmitter and a receiver employ more than one antenna. AMIMO system takes advantage of the spatial diversity or spatialmultiplexing and improves signal-to-noise ratio (SNR) and increasesthroughput.

SFBC is a scheme for transmitting symbols of a space diversity coding onneighboring sub-carriers rather than on the same sub-carrier in thesuccessive time slots. The SFBC avoids the problems of fast timevariations associated with space time block coding (STBC). However, thechannel needs to be constant over the sub-carriers that combining takesplace.

SUMMARY

The present invention is related to a method and apparatus for combiningSFBC, SM and beamforming in a MIMO-OFDM system. The system includes atransmitter with a plurality of transmit antennas and a receiver with aplurality of receive antennas. The transmitter generates at least onedata stream and a plurality of spatial streams. The number of generatedspatial streams is based on the number of the transmit antennas and thenumber of the receive antennas. The transmitter determines atransmission scheme in accordance with at least one of SFBC, SM and beamforming. The transmitter transmits data in the data stream to thereceiver based on the selected transmission scheme.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description, given by way of example and to be understood inconjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of an OFDM-MIMO system implementing a closedloop mode in accordance with the present invention; and

FIG. 2 is a block diagram of an OFDM-MIMO system implementing an openloop mode in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described with reference to the drawingfigures wherein like numerals represent like elements throughout.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

The present invention provides a plurality of combinations of SFBC, SM,FD and beam selection according to the number of available data streamsand spatial streams and the number of transmit and receive antennas. Thecombinations provide flexibility on the design of MIMO-OFDM systems andscalable solutions for any number transmit and receive antennaconfiguration. Each combination has trade-offs between performance,reliability and data rate. Therefore, a combination can be chosenaccording to some criteria, such as robustness, a data rate, a channelcondition, or the like. The number of data streams is preferably decidedbased on a modulation and coding scheme. The number of spatial streamsis decided by the number of transmit and receive antennas.

There are two modes of operation of the system: a closed loop and anopen loop. The closed loop is used when channel state information (CSI)is available to the transmitter. The open loop is used when CSI is notavailable at the transmitter. A variant may be used for transmission tolegacy STA where it provides diversity benefits.

In the closed loop mode, CSI is used to create virtually independentchannels by decomposing and diagonalizing the channel matrix byprecoding at the transmitter and further antenna processing at thereceiver. Given the eigenvalue spread of wireless channels, a trade-offis made between a data rate and robustness by employing SFBC and/or SM.This scheme allows for a simple receiver implementation, simpler than aMinimum Mean Square Error (MMSE) receiver. The combined solution enableshigher throughput over a larger range compared to traditionaltechniques. The technique allows per sub-carrier power/bit loading andmaintains a sustained robust link through closed loop operation with CSIfeedback. Another benefit of the technique is that it is easily scalableto any number of antennas at both transmitter and receiver.

The CSI can be obtained at the transmitter either by feedback from thereceiver or through exploiting channel reciprocity. Latency requirementsand feedback data rates are typically not significant to the inherentfrequency non-selectivity of eigenvalues. A transmit antenna calibrationscheme is required. In addition, channel quality information (CQI) isused to determine a coding rate and a modulation scheme per sub-carrieror group of sub-carriers. The determined coding rate and modulationscheme determines the number of data streams. According to the number ofdata streams, the combinations are chosen with the available spatialstreams.

FIG. 1 is a block diagram of an OFDM-MIMO system 100 implementing aclosed loop mode in accordance with the present invention. The system100 includes a transmitter 110 and a receiver 130. The transmitter 110includes a channel coder 112, a multiplexer 114, a power loading unit116, a plurality of optional SFBC units 118, a plurality ofserial-to-parallel (S/P) converters 120, a transmit beamformer 122, aplurality of IFFT units 124 and a plurality of transmit antennas 126.The channel coder 112 codes data preferably in accordance with a CQIwhich is provided by the receiver 130. The CQI is used to determine acoding rate and modulation scheme per sub-carrier or group ofsub-carriers. The coded data stream is multiplexed by the multiplexer114 into two or more data streams 115.

The transmit power level of each data stream 115 is adjusted by thepower loading unit 116 based on feedback 150 provided from the receiver130. The power loading unit 116 adjusts power levels with respect to thedata rate of each eigenbeam to balance the total transmit power over alleigenbeams (or sub-carriers).

The optional SFBC units 118 perform SFBC on the data streams 115. SFBCis performed over eigen-beams and sub-carriers for each data rate thatis transmitted. Eigen-beam and sub-carrier pairs are selected to ensureindependent channels. OFDM symbols are carried on K sub-carriers. Toaccommodate SFBC, the sub-carriers are divided into L pairs ofsub-carriers (or group of sub-carriers). The bandwidth of each group ofsub-carriers should be less than the coherence bandwidth of the channel.However, when combined with eigen-beamforming this restriction isrelaxed due to the frequency insensitivity of the eigen-beams.

The pairs of sub-carrier groups used by the block code are consideredindependent. The following is an example of the Alamouti type SFBCapplied to an OFDM symbol:

$S = {\begin{bmatrix}s_{1} & {- s_{2}^{*}} \\s_{2} & s_{1}^{*}\end{bmatrix}.}$

Once the optional SFBC units 118 construct OFDM symbols for allsub-carriers, the coded blocks are multiplexed by the S/P converters 120and input to the transmit beamformer 122. The transmit beamformer 122distributes eigen-beams to the transmit antennas. The IFFT units 124convert the data in frequency domain to the data in time domain.

The receiver 130 comprises a plurality of receive antennas 128, aplurality of FFT units 132, a receive beamformer 134, a plurality ofoptional SFBC decoding units 136, a demultiplexer 138, a channel decoder144, a channel estimator 140, a CSI generator 142 and a CQI generator146.

The FFT units 132 convert samples received in time domain by theantennas 128 to frequency domain. The receive beamformer 134, theoptional SFBC decoding units 136, the demultiplexer 138 and the channeldecoder 144 process the samples converted to the frequency domain.

The channel estimator 140 generates channel matrix using a trainingsequence transmitted from the transmitter and decomposes the channelmatrix into two beam-forming unitary matrices U and V, (U for transmitand V for receive), and a diagonal matrix D per sub-carrier (or persub-carrier group) by singular value decomposition (SVD) or eigenvaluedecomposition. The CSI generator 142 generates CSI 147 from the channelestimation results and the CQI generator generates a CQI 148 based onthe decoding results. The CSI and the CQI provide feedback 150 from thereceiver 130 to the transmitter 110.

The channel matrix H between nT transmit antennas and nR receiveantennas can be written as follows:

$H = \begin{bmatrix}h_{11} & h_{21} & \ldots & h_{1,{nT}} \\h_{21} & h_{22} & \ldots & h_{2,{nT}} \\\; & \; & \ddots & \vdots \\h_{{nR},1} & h_{{nR},2} & \ldots & h_{{nR},{nT}}\end{bmatrix}$

The channel matrix H is decomposed by SVD as follows:

H=UDV ^(H)

where U and V are unitary matrices and D is a diagonal matrix.UεC^(nRxnR) and VεC^(nTxnT). Then, for transmit symbol vector s,transmit precoding is simply performed as follows:

x=Vs.

The received signal becomes as follows:

y=HVs+n;

where n is the noise introduced in the channel. The receiver completesthe decomposition by using a matched filter:

V ^(H) H ^(H) =V ^(H) VD ^(H) U ^(H) =D ^(H) U ^(H).

After normalizing channel gain for eigenbeams, the estimate of thetransmit symbols s becomes

$\begin{matrix}{\hat{s} = {{\alpha \; D^{H}U^{H}{HVs}} + \eta}} \\{= {s + {\eta.}}}\end{matrix}$

The symbols s is detected without having to perform successiveinterference cancellation or MMSE type detector. D^(H)D is a diagonalmatrix that is formed by eigenvalues of H across the diagonal.Therefore, the normalization factor α=D⁻². U are eigenvectors of HH^(H),V are eigenvectors of H^(H)H and D is a diagonal matrix of singularvalues of H (square roots of eigenvalues of HH^(H)).

If the optional SFBC units 118 and the optional SFBC decoding units 136are removed from the transmitter 110 and the receiver 130, respectively,the transmitter 110 and the receiver 130 may be used for SM.

In the open loop mode, a combination of space-frequency coding andspatial spreading in the transmitter 110 provides diversity withoutrequiring CSI 147. The CQI 148 is used to determine a coding rate andmodulation per sub-carrier or group of sub-carriers. This coding rateand modulation scheme determines the number of data streams. Accordingto the number of data streams, the combinations are chosen with theavailable spatial streams.

FIG. 2 is a block diagram of a system 200 implementing an open loop modein accordance with the present invention. The system 200 includes atransmitter 210 and a receiver 230. In the open loop mode, a combinationof space-frequency coding and spatial spreading in the transmitter 210provides diversity without requiring CSI. A variant of this scheme maybe used when operating with legacy IEEE 802.11a/g user equipment.

The transmitter 210 includes a channel coder 212, a multiplexer 214, apower loading unit 216, a plurality of SFBC units 218, a plurality ofserial-to-parallel (S/P) converters 220, a beamformer network (BFN) 222,a plurality of IFFT units 224 and a plurality of transmit antennas 226.As in the closed loop mode, the channel coder 212 uses CQI to determinecoding rate and modulation per sub-carrier or group of sub-carriers. Thecoded data stream 213 is multiplexed by the multiplexer 214 into two ormore data streams 215. The BFN 222 forms N beams in space, where N isthe number of antennas 226. The beams are pseudo-randomly constructed bythe BFN matrix operation. The independent sub-carrier groups used forthe SFBC coding are transmitted on individual beams.

For legacy support, SFBC coding may not be performed. Instead diversitythrough beam permutation is performed which improves diversity andtherefore the performance of legacy IEEE 802.11a/g user equipment.

The receiver 230 includes a plurality of receive antennas 231, FFT units232, a BFN 234, an SFBC decoding and combining unit 236 and a channeldecoder 238. The FFT units 232 convert samples received in time domainby the receive antennas 231 to frequency domain. The SFBC decoding andcombining unit 236 decodes and combines symbols received fromsub-carrier groups/eigen-beams and converts them from parallel to serialusing a prior knowledge of the constellation size. Symbols are combinedusing MRC. The channel decoder 238 decodes the combined symbol andgenerates a CQI 240.

If the SFBC units 218 and the SFBC decoding function of the SBC decodingand combining unit 236 are removed from the transmitter 210 and thereceiver 230, respectively, the transmitter 210 and the receiver 230 maybe used for SM.

Examples of SFBC, SM, FD and beam selection combinations in accordancewith the present invention are explained hereinafter.

S_(i) denotes the group of the modulated symbols. The length depends onhow many groups the sub-carriers for data are divided into. Sub-carriersare divided into two groups. Each S_(i) includes symbols whose length isa half of the number of sub-carriers for data.

d_(n) denotes singular values of the channel matrix, where d₁>d₂>d₃> . .. >d_(M), M is the maximum number of the singular values, (i.e., thenumber of transmit antennas).

Rate=1 means that M symbols are sent and recovered per one sub-carrierduring one OFDM symbol duration. When less than M symbols are sent andrecovered, the rate is fractional.

In FD, S_(i) is sent on a half of sub-carriers and S_(i)* is sent on theother half of sub-carriers.

Single Transmit Antenna Case—Single-Input Single-Output (SISO).

In a SISO case, only one data stream and one spatial stream areimplemented. Without using FD, one symbol is sent per sub-carrier. UsingFD, one symbol is sent per two sub-carriers. It is summarized in Table1.

TABLE 1 Spatial Streams SISO (Without FD) SISO (With FD) Stream 1 S1, S2S1, S1* Rate 1 ½

Two Transmit Antenna Case.

With two transmit antennas, a 2×1 or a 2×2 MIMO-OFDM system may besupported, and either one or two data streams may be supported.

2×1 MIMO-OFDM Closed Loop—One Data Stream Case.

In a closed loop mode, beam selection with or without FD and SFBC may beused. Since data transmitted on the beam having smaller singular valuewill die, one beam is selected through SVD. The SVD beam having a largersingular value is chosen. For a beam selection without FD, one datasymbol is sent per a sub-carrier and for a beam selection with FD, onedata symbol is sent per two sub-carriers. In a beam selection with FD,the rate is a half of that in the beam selection without FD case, butthe reliability is increased.

Although the data transmitted on the beam having smaller singular valuewill die, two symbols can be sent at the same time by using SFBC throughtwo sub-carriers. Using this scheme, one data symbol is sent persub-carrier. Comparing with the beam selection case, the performance ofthis case will be degraded, since the second stream with the smallersingular value includes only noise.

One data stream case for the 2×1 MIMO-OFDM closed loop is summarized inTable 2.

TABLE 2 Beam Selection Beam Selection Spatial Streams (Without FD) (WithFD) SFBC Stream 1 (d1) S1, S2 S1, S1* S1, −S2* Stream 2 (d2 = 0) S2, S1*Rate ½ ¼ ½

2×1 MIMO-OFDM Open Loop—One Data Stream Case.

In an open loop mode, SM with or without FD and SFBC may be used. For SM(with the fixed beamforming matrix) without FD, one data symbol is sentper sub-carrier for each spatial stream by using the fixed beamformingand SM, and for SM with FD, one data symbol is sent per two sub-carriersfor each spatial stream by using the fixed beamforming and SM.

Combination of FD and non-FD is possible. In such case, one symbol issent on two sub-carriers on one spatial stream and one symbol is sent onone sub-carrier on the other spatial stream. The data rate is ¾ of theSM without FD case.

If SFBC with the fixed beamforming matrix is used, two data symbols ofthe data stream are sent on two sub-carriers through two antennas byusing the fixed beamforming. The data rate is a half of the SMwithout-FD case.

One data stream case for the 2×1 MIMO-OFDM open loop is summarized inTable 3.

TABLE 3 Spatial SM SM SM Streams (Without FD) (With FD) (FD + non-FD)SFBC Stream 1 S1, S2 S1, S1* S1, S1* S1, −S2* Stream 2 S3, S4 S2, S2*S2, S3 S2, S1* Rate 1 ½ ¾ ½

2×1 MIMO-OFDM (Open Loop)—Two Data Stream Case.

For two data stream case, an open loop mode should be used since an SVDbeam having a smaller singular value carries nothing but noise and willdie, as explained hereinbefore. Without FD, one data symbol is sent persub-carrier for each spatial stream and with FD, one data symbol is sentper two sub-carriers for each spatial stream. Combination of FD andnon-FD is possible.

Two data stream case for the 2×1 MIMO-OFDM open loop is summarized inTable 4.

TABLE 4 Spatial Streams SM (Without FD) SM (FD + non-FD) SM (With FD)Stream 1 S1, S2 S1, S1* S1, S1* Stream 2 S3, S4 S2, S3 S2, S2* Rate 1 ¾½

2×2 MIMO-OFDM Closed Loop—One Data Stream Case.

In a closed loop mode, SM with or without FD, beam selection with orwithout FD and SFBC may be used. In a closed loop mode, two spatialbeams are formed by SVD for each sub-carrier.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers by using one spatial stream. Combination of FD and non-FDis possible.

For beam selection, one SVD beam between two beams for each sub-carrieris selected, which has larger singular value, and the other beam of eachsub-carrier is discarded. For beam selection without FD, one data symbolis sent per one sub-carrier by using one spatial stream. For beamselection with FD, one data symbol is sent per two sub-carriers by usingone spatial stream.

Two spatial streams for each sub-carrier are generated according to theSVD of the channel of each sub-carrier and two data symbols can be senton two sub-carriers by using SFBC.

One data stream case for the 2×2 MIMO-OFDM closed loop is summarized inTable 5.

TABLE 5 SM + SM + Beam Beam SVD SM + SVD Selection Selection Spatial(Without SVD (FD + (Without (With Streams FD) (With FD) non-FD) FD) FD)SFBC Stream 1 (d1) S1, S2 S1, S1* S1, S2 S1, S2 S1, S1* S1, −S2* Stream2 (d2) S3, S4 S2, S2* S3, S3* S2, S1* Rate 1 ½ ¾ ½ ¼ ½

2×2 MIMO-OFDM Open Loop—One Data Stream Case.

In an open loop, SM with or without FD and SFBC may be supported. SM isimplemented with a fixed beamforming matrix and both spatial streams ofeach sub-carrier may be used.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers by using one spatial stream. Combination of FD and non-FDis possible.

Two data symbols of the data stream can be sent on two sub-carriers foreach spatial stream by using the fixed beamforming and SFBC.

The transmitting method is same as one for the 2×1 system. However, theperformance will be better, since two receive antennas are used in areceiver.

One data stream case for the 2×2 MIMO-OFDM open loop is summarized inTable 6.

TABLE 6 Spatial SM SM SM Streams (Without FD) (With FD) (FD + non-FD)SFBC Stream 1 S1, S2 S1, S1* S1, S2 S1, −S2* Stream 2 S3, S4 S2, S2* S3,S3* S2, S1* Rate 1 ½ ¾ ½

2×2 MIMO-OFDM Closed Loop—Two Data Stream Case.

In a closed loop mode, SM with or without FD may be used. SM isperformed with SVD beamforming and two spatial streams are available foreach sub-carrier. Since there are two data streams, one spatial streamshould be assigned to each data stream, and SFBC is not possible for thesame reason.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers by using one spatial stream. Combination of FD and non-FDis possible.

Two data stream case for the 2×2 MIMO-OFDM closed loop is summarized inTable 7.

TABLE 7 SM + SVD SM + SVD SM (FD + Spatial Streams (Without FD) (WithFD) non-FD) Stream 1 (d1) S1, S2 S1, S1* S1, S2 Stream 2 (d2) S3, S4 S2,S2* S3, S3* Rate 1 ½ ¾

2×2 MIMO-OFDM Open Loop—Two Data Stream Case.

In an open loop, SM is implemented with the fixed beamforming matrix andtwo spatial streams are available for each sub-carrier. As explainedhereinbefore, one spatial stream is assigned to each data stream.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers by using one spatial stream. Combination of FD and non-FDis possible.

Two data stream case for the 2×2 MIMO-OFDM open loop is summarized inTable 8.

TABLE 8 Spatial SM SM SM (FD + Streams (Without FD) (With FD) non-FD)Stream 1 S1, S2 S1, S1* S1, S1* Stream 2 S3, S4 S2, S2* S2, S3 Rate 1 ½¾

Three Transmit Antenna Case.

With three transmit antennas, 3×1, 3×2 and 3×3 MIMO-OFDM systems may besupported, and either one, two or three data streams may be supported.

3×1 MIMO-OFDM Closed Loop—One Data Stream Case.

In a closed loop mode, beam selection with or without FD and SFBC may beused. Beams are generated with SVD beam forming, and for beam selection,one spatial beam is selected (only one beam is available since two otherbeams do not carry nothing but noise and will die). The beam having thelargest singular value is selected.

For beam selection without FD, one data symbol is sent per onesub-carrier for the chosen spatial stream and for beam selection withFD, one data symbol is sent per two sub-carriers for the chosen spatialstream.

For SFBC with SVD beamforming, two spatial streams are selected for eachsub-carrier: one corresponding to the largest singular value and theother one corresponding to one of the rest. However, even though twosymbols can be sent at the same time by using SFBC through twosub-carriers, the performance will be very low, since one spatial streamincludes only noise.

One data stream case for the 3×1 MIMO-OFDM closed loop is summarized inTable 9.

TABLE 9 Beam Selection Beam Selection Spatial Streams (Without FD) (WithFD) SFBC Stream 1 (d1) S1, S2 S1, S1* S1, −S2* Stream 2 (d2 = 0) S2, S1*Stream 3 (d3 = 0) Rate ⅓ ⅙ ⅓

3×1 MIMO-OFDM Open Loop—One Data Stream Case.

In an open loop case, SM and SFBC are implemented with the fixedbeamforming matrix and three spatial streams are available.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. Combination of FD and non-FD ispossible. One data symbol is sent per two sub-carriers on one spatialstream and one symbol is sent per one sub-carrier on two other spatialstreams, or one data symbol is sent per two sub-carriers on two spatialstreams and one symbol is sent per one sub-carrier on the other spatialstream.

SFBC may be implemented with or without FD. Among three spatial streamsfor each sub-carrier, two spatial streams are used for SFBC and theother one is used for independent data symbol. Therefore, three symbolscan be sent for each sub-carrier at each instant.

One data stream case for the 3×1 MIMO-OFDM open loop is summarized inTable 10.

TABLE 10 SM SM (FD + SM (FD + SFBC + Spatial (Without SM non-FD non-FDWithout SFBC + Streams FD) (With FD) (case 1) (case 2) FD With FD Stream1 S1, S2 S1, S1* S1, S2 S1, S2 S1, −S2* S1, −S2* Stream 2 S3, S4 S2, S2*S3, S3* S3, S4 S2, S1* S2, S1* Stream 3 S5, S6 S3, S3* S4, S4* S5, S5*S3, S4 S3, S3* Rate 1 ½ ⅔ ⅚ ⅔ ½

3×1 MIMO-OFDM (open loop)—two data stream case.

In this case, an open loop structure should be used to send and recovertwo data streams. SM and SFBC are implemented with the fixed beamformingmatrix and two data streams are divided into three spatial streams foreach sub-carrier.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. Combination of FD and non-FD ispossible.

With SFBC, one data stream is sent and recovered by using SFBC and theother data stream does not use SFBC. Among three spatial streams foreach sub-carrier, two spatial streams are used for SFBC and the otherone is for the other data stream.

Two data stream case for the 3×1 MIMO-OFDM open loop is summarized inTable 11.

TABLE 11 SM SM (FD + SM (FD + SFBC + Spatial (Without SM non-FD non-FDWithout SFBC + Streams FD) (With FD) (case 1) (case 2) FD With FD Stream1 S1, S2 S1, S1* S1, S2 S1, S2 S1, −S2* S1, −S2* Stream 2 S3, S4 S2, S2*S3, S3* S3, S4 S2, S1* S2, S1* Stream 3 S5, S6 S3, S3* S4, S4* S5, S5*S3, S4 S3, S3* Rate 1 ½ ⅔ ⅚ ⅔ ½

3×1 MIMO-OFDM (Open Loop)—Three Data Stream Case.

In this case, an open loop structure should be used to send and recoverthree data streams. SM and SFBC are implemented with the fixedbeamforming matrix and three data streams are divided into three spatialstreams for each sub-carrier and SFBC is not possible in this case.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. Combinations of FD and non-FD arepossible.

Three data stream case for the 3×1 MIMO-OFDM open loop is summarized inTable 12.

TABLE 12 SM (FD + SM (FD + Spatial SM SM non-FD non-FD Streams (WithoutFD) (With FD) (case 1) (case 2) Stream 1 S1, S2 S1, S1* S1, S2 S1, S2Stream 2 S3, S4 S2, S2* S3, S3* S3, S4 Stream 3 S5, S6 S3, S3* S4, S4*S5, S5* Rate 1 ½ ⅔ ⅚

3×2 MIMO-OFDM Closed Loop—One Data Stream Case.

Two spatial streams are available for this case. Two beams are selectedamong three beams for each sub-carrier generated through SVD. Two SVDbeams having larger singular values are selected.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. A combination of FD and non-FD ispossible.

For SFBC, two spatial streams for each sub-carrier are selected and twosymbols are sent at the same time by using SFBC through twosub-carriers. Using this scheme, two data symbol can be recovered pertwo sub-carriers.

One data stream case for the 3×2 MIMO-OFDM closed loop is summarized inTable 13.

TABLE 13 Spatial SM (With- SM (With SM (FD + Streams out FD) FD) non-FD)SFBC Stream 1 (d1) S1, S2 S1, S1* S1, S2 S1, −S2* Stream 2 (d2) S3, S4S2, S2* S3, S3* S2, S1* Stream 3 (d3 = 0) Rate ⅔ ⅓ ½ ⅓

3×2 MIMO-OFDM Open Loop—One Data Stream Case.

The 3×2 open loop case for one data stream is same to the 3×1 open loopcase for one data stream.

3×2 MIMO-OFDM closed loop—two data stream case.

Two spatial streams are available for this case. Two beams among threebeams for each sub-carrier generated through SVD are selected. Two SVDbeams having larger singular values are selected.

For SM without FD, one data symbol is sent per one sub-carrier for eachspatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. A combination of FD and non-FD ispossible.

Two data stream case for the 3×2 MIMO-OFDM closed loop is summarized inTable 14.

TABLE 14 Spatial SM SM SM Streams (Without FD) (With FD) (FD + non-FD)Stream 1 (d1) S1, S2 S1, S1* S1, S2 Stream 2 (d2) S3, S4 S2, S2* S3, S3*Stream 3 (d3 = 0) Rate ⅔ ⅓ ½

3×2 MIMO-OFDM Open Loop—Two Data Stream Case.

The 3×2 open loop case for two data streams is same to the 3×1 open loopcase for two data streams.

3×2 MIMO-OFDM—Three Data Stream Case.

A 3×2 MIMO-OFDM system for three data streams is same to the 3×1MIMO-OFDM system for three data streams.

3×3 MIMO-OFDM Closed Loop—One Data Stream Case.

In a closed loop case, three spatial streams are available. For SMwithout FD, one data symbol is sent per one sub-carrier for each spatialstream, and for SM with FD, one data symbol is sent per two sub-carriersfor each spatial stream. Combinations of FD and non-FD are possible.

For SFBC, two spatial streams among three spatial streams are selected.Preferably, two bad spatial streams for each sub-carrier are selected,which have smaller singular values. Two symbols are sent at the sametime by using SFBC on the two bad spatial streams of two sub-carriers.For the other good stream for each carrier, one data symbol is sentwithout SFBC.

For the non-SFBC spatial stream, if FD is used, one data symbol is sentper one sub-carrier for this spatial stream and if FD is not used, onedata symbol is sent per two sub-carriers for this spatial stream.

One data stream case for the 3×3 MIMO-OFDM closed loop is summarized inTable 15.

TABLE 15 SM SM SM (FD + SM (FD + SFBC + SFBC + Spatial (Without (Withnon-FD non-FD Without With Streams FD) FD) (case 1) (case 2) FD FDStream 1 (d1) S1, S2 S1, S1* S1, S2 S1, S2 S1, S2 S1, S1* Stream 2 (d2)S3, S4 S2, S2* S3, S3* S3, S4 S3, −S4* S2, −S3* Stream 3 (d3) S5, S6 S3,S3* S4, S4* S5, S5* S4, S3* S3, S2* Rate 1 ½ ⅔ ⅚ ⅔ ½

3×3 MIMO-OFDM Open Loop—One Data Stream Case.

In an open loop case, all the options for 3×1 open loop case for onedata stream may be used.

3×3 MIMO-OFDM Closed Loop—Two Data Stream Case.

Three spatial streams are available for this case and two data streamsare divided into three spatial streams for each sub-carrier. In a closedloop, for SM without FD, one data symbol is sent per one sub-carrier foreach spatial stream, and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. Combinations of FD and non-FD arepossible.

For SFBC, two spatial streams are selected among three spatial streams.Preferably, two bad spatial streams for each sub-carrier are selected,which have smaller singular values. For one data stream, two symbols aresent at the same time by using SFBC on two bad spatial streams of twosub-carriers, and for the other good stream for each carrier, the otherdata stream is sent without SFBC.

For the non-SFBC spatial stream, without FD, one data symbol is sent perone sub-carrier for this spatial stream, and with FD, one data symbol issent per two sub-carriers for this spatial stream.

Two data stream case for the 3×3 MIMO-OFDM closed loop is summarized inTable 16.

TABLE 16 SM SM SM (FD + SM (FD + SFBC + Spatial (Without (With non-FDnon-FD Without SFBC + Streams FD) FD) (case 1) (case 2) FD With FDStream 1 (d1) S1, S2 S1, S1* S1, S2 S1, S2 S1, S2 S1, S1* Stream 2 (d2)S3, S4 S2, S2* S3, S3* S3, S4 S3, −S4* S2, −S3* Stream 3 (d3) S5, S6 S3,S3* S4, S4* S5, S5* S4, S3* S3, S2* Rate 1 ½ ⅔ ⅚ ⅔ ½

3×3 MIMO-OFDM Open Loop—Two Data Stream Case.

In an open loop case, all the options for 3×1 open loop case for twodata streams may be used.

3×3 MIMO-OFDM Closed Loop—Three Data Stream Case.

Three spatial streams are available for this case and three data streamsare divided into three spatial streams for each sub-carrier. In a closedloop, for SM without FD, one data symbol is sent per one sub-carrier foreach spatial stream and for SM with FD, one data symbol is sent per twosub-carriers for each spatial stream. Combinations of FD and non-FD arepossible.

Two data stream case for the 3×3 MIMO-OFDM closed loop is summarized inTable 17.

TABLE 17 Spatial SM (With- SM (With SM (FD + SM (FD + Streams out FD)FD) non-FD 1) non-FD 2) Stream 1 (d1) S1, S2 S1, S1* S1, S2 S1, S2Stream 2 (d2) S3, S4 S2, S2* S3, S3* S3, S4 Stream 3 (d3) S5, S6 S3, S3*S4, S4* S5, S5* Rate 1 ½ ⅔ ⅚

3×3 MIMO-OFDM closed loop—three data stream case.

In an open loop case, all the options for 3×1 open loop case for threedata streams may be used.

Four Transmit Antenna Case.

With four transmit antennas, 4×1, 4×2, 4×3 and 4×4 MIMO-OFDM systems maybe supported, and either one, two, three or four data streams may besupported.

4×1 MIMO-OFDM Closed Loop—One Data Stream Case.

Only one spatial stream is available for this case. In a closed loopcase, one beam among four beams for each sub-carrier generated throughSVD is selected. The SVD beam having the largest singular value isselected.

For SM without FD, one data symbol is sent per one sub-carrier for thespatial stream and for SM with FD, one data symbol is sent per twosub-carriers for the spatial stream.

For SFBC with SVD beamforming, two spatial streams for each sub-carrierare selected among four beams generated through SVD. One corresponds tothe largest singular value and the other corresponds to one of the rest.Although two symbols can be sent at the same time by using SFBC throughtwo sub-carriers, the performance will be low, since the bad spatialstream includes only noise.

One data stream case for the 4×1 MIMO-OFDM closed loop is summarized inTable 18.

TABLE 18 Spatial SM SM Streams (Without FD) (With FD) SFBC Stream 1 (d1)S1, S2 S1, S1* S1, −S2* Stream 2 (d2 = 0) S2, S1* Stream 3 (d3 = 0)Stream 4 (d4 = 0) Rate ¼ ⅛ ¼

4×1 MIMO-OFDM Open Loop—One Data Stream Case.

SM is implemented with the fixed beamforming matrix and four spatialstreams are available.

For SM without FD, one data symbol is sent per one sub-carrier for thespatial stream and for SM with FD, one data symbol is sent per twosub-carriers for the spatial stream. Combinations of FD and non-FD arepossible as shown in Table 19 below. For one data stream, thesecombinations may not be used to maintain same quality for all datasymbols.

Combination of SM and SFBC with the fixed beamforming matrix arepossible. A first option is one 2×2 SFBC and two SM. For one datastream, this option may not used to maintain same quality for all datasymbols. The other two spatial streams of each sub-carrier are used forSM of another two data symbols of the data stream. Without FD, one datasymbol is sent per one sub-carrier for each spatial stream and with FD,one data symbol is sent per two sub-carriers for each spatial stream.Combinations of FD and non-FD are possible as shown in Table 20.

A second option is using two 2×2 SFBC. Four spatial streams of eachsub-carrier are divided into two groups of two streams and each group isassigned to each SFBC. For each instant, four (4) data symbols are senton two sub-carriers by using the fixed beamforming and two 2×2 SFBCs.

TABLE 19 Spatial SM (With- SM (With SM (FD + SM (FD + SM (FD + Streamsout FD) FD) non-FD 1) non-FD 2) non-FD 3) Stream 1 S1, S2 S1, S1* S1, S2S1, S2 S1, S2 Stream 2 S3, S4 S2, S2* S3, S3* S3, S4 S3, S4 Stream 3 S5,S6 S3, S3* S4, S4* S5, S5* S5, S6 Stream 4 S7, S8 S4, S4* S5, S5* S6,S6* S7, S7* Rate 1 ½ ⅝ ¾ ⅞

TABLE 20 Spatial SFBC (With- SFBC (With SFBC (FD + Two Streams out FD)FD) non-FD SFBC Stream 1 S1, S2 S1, S1* S1, S2 S1, −S2* Stream 2 S3, S4S2, S2* S3, S3* S2, S1* Stream 3 S5, −S6* S3, −S4* S4, −S5* S3, −S4*Stream 4 S6, S5* S4, S3* S5, S4* S4, S3* Rate ¾ ½ ⅝ ½

4×1 MIMO-OFDM (Open Loop)—Two Data Stream Case.

In this case, an open loop should be used to send and recover the twodata streams. SM is implemented with the fixed beamforming matrix andtwo data streams are divided into four spatial streams for eachsub-carrier.

For SM without FD, one data symbol is sent per one sub-carrier for thespatial stream and for SM with FD, one data symbol is sent per twosub-carriers for the spatial stream. Combinations of FD and non-FD arepossible as shown in Table 21. The combination cases 1 and 3 in Table 21may not used to maintain the same quality for each data symbol of eachdata stream.

Combination of SM and SFBC with the fixed beamforming matrix ispossible. A first option is one 2×2 SFBC and two SM. One data stream isassigned to the SFBC and the other data stream is sent by SM. Twospatial streams of each sub-carrier are used for SFBC and the other twospatial streams of each sub-carrier are used for SM. Without FD, onedata symbol is sent per one sub-carrier for each spatial stream, andwith FD, one data symbol is sent per two sub-carriers for each spatialstream. A combination of FD and non-FD is possible as shown in Table 22.This combination may not used to maintain the same quality for each datasymbol of the data stream, which uses SM.

A second option is using two 2×2 SFBCs. Each data stream is assigned tothe separate 2×2 SFBC. Four spatial streams of each sub-carrier aredivided into two groups of two streams and each group is assigned toeach SFBC. For each instant, 2 data symbols of each data stream are senton two sub-carriers by using the fixed beamforming and each 2×2 SFBCs.

TABLE 21 Spatial SM (With- SM (With SM (FD + SM (FD + SM (FD + Streamsout FD) FD) non-FD 1) non-FD 2) non-FD 3) Stream 1 S1, S2 S1, S1* S1, S2S1, S2 S1, S2 Stream 2 S3, S4 S2, S2* S3, S3* S3, S4 S3, S4 Stream 3 S5,S6 S3, S3* S4, S4* S5, S5* S5, S6 Stream 4 S7, S8 S4, S4* S5, S5* S6,S6* S7, S7* Rate 1 ½ ⅝ ¾ ⅞

TABLE 22 Spatial SFBC (With- SFBC (With SFBC (FD + Two Streams out FD)FD) non-FD SFBC Stream 1 S1, S2 S1, S1* S1, S2 S1, −S2* Stream 2 S3, S4S2, S2* S3, S3* S2, S1* Stream 3 S5, −S6* S3, −S4* S4, −S5* S3, −S4*Stream 4 S6, S5* S4, S3* S5, S4* S4, S3* Rate ¾ ½ ⅝ ½

4×1 MIMO-OFDM (Open Loop)—Three Data Stream Case.

In this case, an open loop should be used to send and recover three datastreams. SM is implemented with the fixed beamforming matrix and threedata streams are divided into four data symbols for each sub-carrier.All the combinations in Table 21 can be used.

Combination of SM and SFBC with the fixed beamforming matrix ispossible. A first option is using one 2×2 SFBC and two SMs. Two spatialstreams of each sub-carrier are used for SFBC. One data stream is sentusing this SFBC and the fixed beamforming and the other two spatialstreams of each sub-carrier are used for SM of the other two datastreams. Without FD, one data symbol is sent per one sub-carrier foreach spatial stream, and with FD, one data symbol is sent per twosub-carriers for each spatial stream. A combination of FD and non-FD ispossible as shown in Table 23.

Three data stream case for the 4×1 MIMO-OFDM open loop for SFBC issummarized in Table 23.

TABLE 23 Spatial SFBC SFBC SFBC Streams (Without FD) (With FD) (FD +non-FD Stream 1 S1, S2 S1, S1* S1, S2 Stream 2 S3, S4 S2, S2* S3, S3*Stream 3 S5, −S6* S3, −S4* S4, −S5* Stream 4 S6, S5* S4, S3* S5, S4*Rate ¾ ½ ⅝

4×1 MIMO-OFDM (Open Loop)—Four Data Stream Case.

In this case an open loop should be used to send and recover four datastreams. SM is implemented with the fixed beamforming matrix and fourdata streams are divided into four spatial streams for each sub-carrier.All the methods in Table 21 can be used.

4×2 MIMO-OFDM Closed Loop—One Data Stream Case.

Only two spatial streams are available for this case. Two beams areselected among four beams for each sub-carrier generated through SVD.Two SVD beams having larger singular values are selected. For SM withoutFD, one data symbol is sent per one sub-carrier for the spatial streamand for SM with FD, one data symbol is sent per two sub-carriers for thespatial stream. Combinations of FD and non-FD are possible as shown inTable 24.

For SFBC, two spatial streams for each sub-carrier are selected, whichhave larger singular values. Two symbols are sent at the same time byusing SFBC through two sub-carriers. Using this scheme, two data symbolare recovered per two sub-carriers at each instant.

One data stream case for the 4×2 MIMO-OFDM closed loop is summarized inTable 24.

TABLE 24 Spatial SM (With- SM (With SM (FD + Streams out FD) FD) non-FD)SFBC Stream 1 (d1) S1, S2 S1, S1* S1, S2 S1, −S2* Stream 2 (d2) S3, S4S2, S2* S3, S3* S2, S1* Stream 3 (d3 = 0) Stream 4 (d4 = 0) Rate ½ ¼ ⅜ ¼

4×2 MIMO-OFDM Open Loop—One Data Stream Case.

In this case, all the options for 4×1 open loop case for one data streammay be used.

4×2 MIMO-OFDM Closed Loop—Two Data Stream Case.

Two spatial streams are available for this case. Two beams are selectedamong four beams for each sub-carrier generated through SVD. Two SVDbeams having larger singular values are selected. Without FD, one datasymbol is sent per one sub-carrier for each spatial stream, and with FD,one data symbol is sent per two sub-carriers for each spatial stream. Acombination of FD and non-FD is possible.

Two data stream case for the 4×2 MIMO-OFDM closed loop is summarized inTable 25.

TABLE 25 Spatial SM SM SM Streams (Without FD) (With FD) (FD + non-FD)Stream 1 (d1) S1, S2 S1, S1* S1, S2 Stream 2 (d2 = 0) S3, S4 S2, S2* S3,S3* Stream 3 (d3 = 0) Stream 4 (d4 = 0) Rate ½ ¼ ⅜

4×2 MIMO-OFDM open loop—two data stream case. In this case, all theoptions for 4×1 for two data streams may be used.

4×2 MIMO-OFDM—three data stream case. In this case, all the options for4×1 for three data streams may be used.

4×2 MIMO-OFDM—four data stream case. In this case, all the options for4×1 for four data streams may be used.

4×3 MIMO-OFDM Closed Loop—One Data Stream Case.

SM is implemented with SVD beamforming and three spatial streams areavailable for this case. Three spatial streams that have larger singularvalues are selected. Without FD, one data symbol is sent per onesub-carrier for each spatial stream, and with FD, one data symbol issent per two sub-carriers for each spatial stream. Combinations of FDand non-FD are possible as shown in Table 26.

For SFBC, three spatial streams for each sub-carrier are selected, whichhave larger singular values. Among them, two spatial streams, preferablytwo bad spatial streams, are assigned for SFBC. Two symbols are sent atthe same time by using SFBC on two bad spatial streams of twosub-carriers, and for the best spatial stream of each carrier, one datasymbol is sent without SFBC. For the latter spatial stream, without FD,one data symbol is sent per one sub-carrier for each spatial stream, andwith FD, one data symbol is sent per two sub-carriers for each spatialstream.

One data stream case for the 4×3 MIMO-OFDM closed loop is summarized inTable 26.

TABLE 26 SM SM SM SM (Without (With (FD + (FD + SFBC + SFBC + SpatialStreams FD) FD) non-FD) non-FD) non-FD FD Stream 1 (d1) S1, S2 S1, S1*S1, S2 S1, S2 S1, S2 S1, S1* Stream 2 (d2) S3, S4 S2, S2* S3, S4 S3, S3*S3, −S4* S2, −S3* Stream 3 (d3) S5, S6 S3, S3* S5, S5* S4, S4* S4, S3*S3, S2* Stream 4 (d4 = 0) Rate ¾ ⅜ ⅝ ½ ½ ⅜

4×3 MIMO-OFDM open loop—one data stream case. In this case, all theoptions for 4×1 for one data stream case may be used.

4×3 MIMO-OFDM Closed Loop—Two Data Stream Case.

SM is implemented with SVD beamforming and three spatial streams areavailable for this case. Two data streams are divided into three spatialstreams for each sub-carrier. All the SM methods in Table 26 can beapplied to this case.

For SFBC, one data stream is sent by using SFBC. Three spatial streamsfor each sub-carrier are selected, which have larger singular values.Among them, two spatial streams, preferably two bad spatial streams, foreach sub-carrier are assigned for SFBC. Two symbols are sent at the sametime by using SFBC on two bad spatial streams of two sub-carriers.

The other stream is sent by using SM. All the methods for SFBC in Table26 can be used for this case.

Two data stream case for the 4×3 MIMO-OFDM closed loop is summarized inTable 27.

TABLE 27 SM SM SM SM (Without (With (FD + (FD + SFBC + SFBC + SpatialStreams FD) FD) non-FD) non-FD) non-FD FD Stream 1 (d1) S1, S2 S1, S1*S1, S2 S1, S2 S1, S2 S1, S1* Stream 2 (d2) S3, S4 S2, S2* S3, S4 S3, S3*S3, −S4* S2, −S3* Stream 3 (d3) S5, S6 S3, S3* S5, S5* S4, S4* S4, S3*S3, S2* Stream 4 (d4 = 0) Rate ¾ ⅜ ⅝ ½ ½ ⅜

4×3 MIMO-OFDM open loop—two data stream case. In this case, all theoptions for 4×1 for two data stream case may be used.

4×3 MIMO-OFDM Closed Loop—Three Data Stream Case.

SM is implemented with SVD beamforming and three spatial streams areavailable for this case. Three data streams are divided into threespatial streams for each sub-carrier. Without FD, one data symbol issent per one sub-carrier for each spatial stream, and with FD, one datasymbol is sent per two sub-carriers for each spatial stream.Combinations of FD and non-FD are possible.

Three data stream case for the 4×3 MIMO-OFDM closed loop is summarizedin Table 28.

TABLE 28 Spatial SM (With- SM (With SM (FD + SM (FD + Streams out FD)FD) non-FD) non-FD) Stream 1(d1) S1, S2 S1, S1* S1, S2 S1, S2 Stream2(d2) S3, S4 S2, S2* S3, S4 S3, S3* Stream 3(d3) S5, S6 S3, S3* S5, S5*S4, S4* Stream 4(d4 = 0) Rate ¾ ⅜ ⅝ ½

4×3 MIMO-OFDM open loop—three data stream case. In this case, all theoptions for 4×1 for three data stream case may be used.

4×3 MIMO-OFDM closed loop—four data stream case. In this case, all theoptions for 4×1 for four data stream case may be used.

4×4 MIMO-OFDM Closed Loop—One Data Stream Case.

SM is implemented with SVD beamforming and four spatial streams areavailable for this case. Without FD, one data symbol is sent per onesub-carrier for each spatial stream, and with FD, one data symbol issent per two sub-carriers for each spatial stream. Combinations of FDand non-FD are possible as shown in Table 29.

A first option for SFBC is using one 2×2 SFBC and two SMs. By singularvalues of each sub-carrier, two spatial streams, preferably two badspatial streams having smaller singular values, are selected. On thesetwo bad spatial streams of each sub-carrier, the data symbol is sent byusing SFBC. By using the other two good spatial streams of eachsub-carrier two data symbols are sent by using SM, without SFBC. In thiscase, without FD, one data symbol is sent per one sub-carrier for eachspatial stream, and with FD, one data symbol is sent per twosub-carriers for each spatial stream. A combination of FD and non-FD ispossible as shown in Table 30.

A second option is using two 2×2 SFBCs. Each two data symbols areassigned to the separate 2×2 SFBC. Four spatial streams of eachsub-carrier are divided into two groups of two spatial streams and eachgroup is assigned to each SFBC. For each instant, four (4) data symbolsof the data stream on two sub-carriers are sent by using the SVDbeamforming and two 2×2 SFBCs.

One data stream case for the 4×4 MIMO-OFDM closed loop for SM issummarized in Table 29 and one data stream case for the 4×4 MIMO-OFDMclosed loop for SFBC is summarized in Table 30.

TABLE 29 SM (FD + SM (FD + SM (FD + Spatial SM (With- SM (With non-FDnon-FD non-FD Streams out FD) FD) (case 1) (case 2) (case 3) Stream1(d1) S1, S2 S1, S1* S1, S2 S1, S2 S1, S2 Stream 2(d2) S3, S4 S2, S2*S3, S3* S3, S4 S3, S4 Stream 3(d3) S5, S6 S3, S3* S4, S4* S5, S5* S5, S6Stream 4(d4) S7, S8 S4, S4* S5, S5* S6, S6* S7, S7* Rate 1 ½ ⅝ ¾ ⅞

TABLE 30 Spatial SFBC (With- SFBC (With SFBC (FD + Two Streams out FD)FD) non-FD) SFBC Stream 1(d1) S1, S2 S1, S1* S1, S2 S1, −S2* Stream2(d2) S3, S4 S2, S2* S3, S3* S2, S1* Stream 3(d3) S5, −S6* S3, −S4* S4,−S5* S3, −S4* Stream 4(d4) S6, S5* S4, S3* S5, S4* S4, S3* Rate ¾ ½ ⅝ ½

4×4 MIMO-OFDM open loop—one data stream case. In this case, all theoptions for 4×1 for one data stream case may be used.

4×4 MIMO-OFDM Closed Loop—Two Data Stream Case.

SM is implemented with SVD beamforming and four spatial streams areavailable for this case. Two data streams are divided into four spatialstreams for each sub-carrier. All the methods in Tables 29 and 30 can beused.

4×4 MIMO-OFDM open loop—two data stream case. In this case, all theoptions for 4×1 for two data stream case may be used.

4×4 MIMO-OFDM Closed Loop—Three Data Stream Case.

SM is implemented with SVD beamforming and four spatial streams areavailable for this case. Three data streams are divided into fourspatial streams for each sub-carrier. All the methods in Table 29 can beused.

For SFBC, one 2×2 SFBC and two SMs are used for three data streams. Onedata stream is sent by using the 2×2 SFBC with SVD beamforming. Bysingular values of each sub-carrier, two spatial streams, preferably twobad spatial streams having smaller singular values, are selected. Onthese two bad spatial streams of each sub-carrier, two data symbols ofone data stream on two sub-carriers are sent by using SFBC and SVDbeamforming. The other two data streams are sent by using SM with SVDbeamforming. Using the other two good spatial streams of eachsub-carrier, two data symbols per sub-carrier are sent for the other twodata streams by using SM, without SFBC. In this case, without FD, onedata symbol is sent per one sub-carrier for each spatial stream, andwith FD, one data symbol is sent per two sub-carriers for each spatialstream. A combination of FD and non-FD is possible as shown in Table 31.

Three data stream case for the 4×4 MIMO-OFDM closed loop for SFBC issummarized in Table 31.

TABLE 31 Spatial SFBC SFBC SFBC Streams (Without FD) (With FD) (FB +non-FD Stream 1(d1) S1, S2 S1, S1* S1, S2 Stream 2(d2) S3, S4 S2, S2*S3, S3* Stream 3(d3) S5, −S6* S3, −S4* S4, −S5* Stream 4(d4) S6, S5* S4,S3* S5, S4* Rate ¾ ½ ⅝

4×4 MIMO-OFDM open loop—three data stream case. In this case, all theoptions for 4×1 for three data stream case may be used.

4×4 MIMO-OFDM Closed Loop—Four Data Stream Case.

SM is implemented with SVD beamforming and four spatial streams areavailable for this case. Four data streams are divided into four spatialstreams for each sub-carrier. All the methods in Table 29 can be used.

4×4 MIMO-OFDM open loop—four data stream case. In this case, all theoptions for 4×1 for four data stream case may be used.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

What is claimed is:
 1. A transmitter comprising: four antennas; and circuitry configured to transmit in an orthogonal frequency division multiplex (OFDM) symbol time period using both frequency diversity and space frequency block coding; wherein for frequency diversity at least one first data element is repeated producing at least two second data elements and the two second data elements are transmitted using different subcarriers; wherein for space frequency block coding, a pair of third data elements are space frequency block coded producing four fourth data elements; wherein the four fourth data elements are transmitted using two subcarriers and only two of the four antennas.
 2. The transmitter of claim 1 wherein the at least one first data element and the pair of third data elements relate to data of a same channel.
 3. The transmitter of claim 1 wherein the at least one first data element and the pair of third data elements are derived from different data.
 4. The transmitter of claim 1 wherein the two second data elements are transmitted using different ones of the four antennas than the four fourth data elements.
 5. A receiver comprising: at least one receive antenna; and circuitry configured to receive and recover data in an orthogonal frequency division multiplex (OFDM) symbol time period transmitted using both frequency diversity and space frequency block coding; wherein for frequency diversity at least one first data element is repeated producing at least two second data elements and the two second data elements are transmitted using different subcarriers; wherein for space frequency block coding, a pair of third data elements are space frequency block coded producing four fourth data elements; wherein the four fourth data elements are transmitted using two subcarriers and only two of four antennas.
 6. The receiver of claim 5 wherein the at least one first data element and the pair of third data elements relate to data of a same channel.
 7. The receiver of claim 5 wherein the at least one first data element and the pair of third data elements were derived from different data.
 8. The receiver of claim 5 wherein the two second data elements were transmitted using different ones of the four antennas than the four fourth data elements.
 9. A method comprising: transmitting, by a transmitter, in an orthogonal frequency division multiplex (OFDM) symbol time period using both frequency diversity and space frequency block coding using four antennas; wherein for frequency diversity at least one first data element is repeated producing at least two second data elements and the two second data elements are transmitted using different subcarriers; wherein for space frequency block coding, a pair of third data elements are space frequency block coded producing four fourth data elements; wherein the four fourth data elements are transmitted using two subcarriers and only two of four antennas.
 10. The method of claim 9 wherein the at least one first data element and the pair of third data elements relate to data of a same channel.
 11. The method of claim 9 wherein the at least one first data element and the pair of third data elements are derived from different data.
 12. The method of claim 9 wherein the two second data elements are transmitted using different ones of the four antennas than the four fourth data elements.
 13. A method comprising: receiving and recovering, by a receiver, data in an orthogonal frequency division multiplex (OFDM) symbol time period transmitted using both frequency diversity and space frequency block coding; wherein for frequency diversity at least one first data element was repeated producing at least two second data elements and the two second data elements were transmitted using different subcarriers; wherein for space frequency block coding, a pair of third data elements were space frequency block coded producing four fourth data elements; wherein the four fourth data elements are transmitted using two subcarriers and only two of four antennas.
 14. The method of claim 13 wherein the at least one first data element and the pair of third data elements relate to data of a same channel.
 15. The method of claim 13 wherein the at least one first data element and the pair of third data elements were derived from different data.
 16. The method of claim 13 wherein the two second data elements were transmitted using different ones of the four antennas than the four fourth data elements. 